Since nitrogen monoxide (hereinafter, referred to as NO) was found as the essential component of a muscle relaxant factor, the physiological effect of NO has been elucidated, and hence NO can be used as a neural information transmitter or an infection marker.
In particular, the analysis of the NO gas in the exhaled air has been attracting attention as a marker for nowadays continuously increasing respiratory tract infection, due to asthma or allergy. Such analysis has been also attracting attention because of the capability of noninvasive diagnosis of disease without imposing burden on patients. The NO gas concentration in the exhaled air is 2 ppb to 20 ppb in normal subjects, but is known to increase by a factor of about three in the cases of respiratory tract inflammation such as allergy and asthma. Therefore, the determination of the NO gas in the exhaled air can be utilized for the determination of degree of inflammation of the respiratory tract of a patient or for asthma care guidelines such as the determination of dosage of therapeutic medicine for asthma.
Conventionally, the method for determining NO, to be applied to the exhaled air, has been such that NO collected from the exhaled air of a patient is allowed to react with ozone under reduced pressure, and light emitted during the reaction is detected. However, this chemiluminescence method requires expensive peripheral devices such as an ozone generating device, and the maintenance of such devices is laborious.
Under such circumstances, in order that an asthma patient may determine the NO concentration everyday at a hospital or at home to perform self-administration of asthma, there is a demand for a NO analyzer which is inexpensive, compact, excellent in gas selectivity and high in sensitivity.
Recently, there has been disclosed a method in which a cobalt tetrasulfothienyl porphyrin (hereinafter, referred to as Co{T(5-ST)P}) supported on sol-gel silica is reacted with NO in a vacuum chamber, and NO coordinated to Co{T(5-ST)P} is detected by spectroscopic measurement (see, for example, Non Patent Literature 1).
In this method, the Co{T(5-ST)P} supported on the surface of the sol-gel silica was heated to 200° C. for the purpose of attaining a difference between the reactivity of the nitrogen oxide gas and the reactivity of other gases, and thus 17 ppm of the NO gas was successfully sensed.
There has also been developed a NO sensor in which Ga2O3 is formed by oxidation of Ga on a GaAs field effect transistor, then a monomolecular film of hematoporphyrin IX, protoporphyrin IX, hemin, or cobalt phorphyrin II chloride is formed on the Ga2O3, and the monomolecular film is beforehand provided with a gate potential and is reacted with NO, and from the thus generated electric current change, a NO concentration is determined (see, for example, Patent Literature 1).
There has also been known a method in which in a vacuum chamber, a cobalt tetraphenylporphyrin (5,10,15,20-tetraphenyl-21H,23H-porphyrin cobalt (hereinafter, referred to as CoTPP)) and NO are reacted with each other, and the NO coordinated to the CoTPP is detected by infrared spectroscopic measurement (see, for example, Non Patent Literature 2).
There has also been disclosed a method in which a temperature controller formed of indium tin oxide is provided on the backside of a substrate for the purpose of improving reproducibility, a film containing a benzotriazaporphyrin incorporating a transition metal such as chromium (Cr3+), vanadyl (VO), manganese (Mn), cobalt (Co) and copper (Cu) is formed on the surface of the substrate to fabricate a gas sensor, and the gas sensor is preheated before the sensor is exposed to a gas. The sensor is preheated at 130° C., and the reactivity to a chlorine gas of 250 ppm to 100% in concentration has been measured with a conductivity change. The preheating effect on sensor recovery is as follows: in the case of nonpreheating treatment, the sensor recovery takes 24 hours after the exposure to the gas; in the case of a preheating temperature of 190° C., the sensor is recovered in 4 minutes; with the preheating at such a high temperature of 190° C., the second and later runs of exposure undergo a gradual decrease in the change magnitude of the sensor with respect to a chlorine gas, and thus the sensor is degraded (see, for example, Patent Literature 2).
There has also been disclosed a volatile gas detection method which disposes, for the purpose of determining VOC gas components, a plurality of porphyrins selected from the group consisting of porphyrins each adopting, as a porphyrin central metal, tin (Sn4+), cobalt (Co3+ or Co2+), chromium (Cr3+), iron (Fe3+), ruthenium (Ru2+), zinc (Zn2+) or silver (Ag2+) and a free base porphyrin (with 2H+ instead of a metal) (see, for example, Patent Literature 3).
There have also been disclosed a method and a device for sensing harmful gases such as halogen gases and hydrogen halide gases by using, as a sensing member, a polymer matrix utilizing a free base porphyrin containing no central metal atom or a zinc tetraphenylporphyrin containing zinc (Zn) as a central metal (see, for example, Patent Literature 4).